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The Large Magellanic Cloud, a dwarf galaxy. At a distance of 163,000 light-years, it is the third closest galaxy to the Milky Way.
The Large Magellanic Cloud, a dwarf galaxy. At a distance of 163,000 light-years, it is the third closest galaxy to the Milky Way.

Intergalactic travel is the hypothetical crewed or uncrewed travel between galaxies. Due to the enormous distances between the Milky Way and even its closest neighbors—tens of thousands to millions of light-years—any such venture would be far more technologically demanding than even interstellar travel. Intergalactic distances are roughly a hundred-thousandfold (five orders of magnitude) greater than their interstellar counterparts.[a]

The technology required to travel between galaxies is far beyond humanity's present capabilities, and currently only the subject of speculation, hypothesis, and science fiction.

However, theoretically speaking, there is nothing to conclusively indicate that intergalactic travel is impossible. There are several hypothesized methods of carrying out such a journey, and to date several academics have studied intergalactic travel in a serious manner.[1][2][3]

Possible methods

Hypervelocity stars

See also: Intergalactic star

Theorized in 1988,[4] and observed in 2005,[5] hypervelocity stars move faster than the escape velocity of the Milky Way, and are traveling out into intergalactic space.[6] There are several theories for their existence. One of the mechanisms would be that the supermassive black hole at the center of the Milky Way ejects stars from the galaxy at a rate of about one every hundred thousand years. Another theorized mechanism might be a supernova explosion in a binary system.[7] Intergalactic travel using these stars would involve entering into an orbit around them and waiting for them to reach another galaxy.[8][9]

Artificially propelling a star

See also: Stellar engine

Another proposal is to artificially propel a star in the direction of another galaxy.[10][11]

Time dilation

While it takes light approximately 2.54 million years to traverse the gulf of space between Earth and, for instance, the Andromeda Galaxy, it would take a much shorter amount of time from the point of view of a traveler at close to the speed of light due to the effects of time dilation; the time experienced by the traveler depending both on velocity (anything less than the speed of light) and distance traveled (length contraction). Intergalactic travel for humans is therefore possible, in theory, from the point of view of the traveler.[12] For example, a rocket that accelerated at standard acceleration due to gravity toward the Andromeda Galaxy and started to decelerate halfway through the trip would arrive in about 28 years, from the frame of reference of the observer.[13]

Possible faster-than-light methods

The Alcubierre drive is a hypothetical concept that is able to impulse a spacecraft to speeds faster than light (the spaceship itself would not move faster than light, but the space around it would). This could in theory allow practical intergalactic travel. There is no known way to create the space-distorting wave this concept needs to work, but the metrics of the equations comply with relativity and the limit of light speed.[14]

A wormhole is a hypothetical tunnel through space-time that would allow instantaneous intergalactic travel to the most distant galaxies even billions of light years away. Wormholes are allowed by general relativity.[15]

See also


  1. ^ Burruss, Robert Page; Colwell, J. (September–October 1987). "Intergalactic Travel: The Long Voyage From Home". The Futurist. 21 (5): 29–33.
  2. ^ Fogg, Martyn (November 1988). "The Feasibility of Intergalactic Colonisation and its Relevance to SETI". Journal of the British Interplanetary Society. 41 (11): 491–496. Bibcode:1988JBIS...41..491F.
  3. ^ Armstrong, Stuart; Sandberg, Anders. "Eternity in six hours: intergalactic spreading of intelligent life and sharpening the Fermi paradox" (PDF). Future of Humanity Institute, Philosophy Department, Oxford University. Cite journal requires |journal= (help)
  4. ^ Hills, J. G. (1988). "Hyper-velocity and tidal stars from binaries disrupted by a massive Galactic black hole" (PDF). Nature. 331 (6158): 687–689. Bibcode:1988Natur.331..687H. doi:10.1038/331687a0.
  5. ^ Brown, Warren R.; Geller, Margaret J.; Kenyon, Scott J.; Kurtz, Michael J. (2005). "Discovery of an Unbound Hypervelocity Star in the Milky Way Halo". Astrophysical Journal. 622 (1): L33–L36. arXiv:astro-ph/0501177. Bibcode:2005ApJ...622L..33B. doi:10.1086/429378.
  6. ^ "The Hyper Velocity Star Project: The stars". The Hyper-Velocity Star Project. 6 September 2009. Retrieved 20 September 2014.
  7. ^ Watzke, Megan (28 November 2007). "Chandra discovers cosmic cannonball". Newswise.
  8. ^ Villard, Ray (24 May 2010). "The Great Escape: Intergalactic Travel is Possible". Discovery News. Retrieved October 18, 2010.
  9. ^ Gilster, Paul (26 June 2014). "Intergalactic Travel via Hypervelocity Stars". Retrieved 16 September 2014.
  10. ^ Gilster, Paul (27 June 2014). "Stars as Stellar Engines". Retrieved 16 September 2014.
  11. ^ Gilster, Paul (30 June 2014). "Building the Bowl of Heaven". Retrieved 16 September 2014.
  12. ^ Gilster, Paul (25 June 2014). "Sagan's Andromeda Crossing". Retrieved 16 September 2014.
  13. ^ "The Relativistic Rocket". Retrieved 4 April 2018.
  14. ^ Alcubierre, Miguel (1994). "The warp drive: hyper-fast travel within general relativity". Classical and Quantum Gravity. 11 (5): L73–L77. arXiv:gr-qc/0009013. Bibcode:1994CQGra..11L..73A. doi:10.1088/0264-9381/11/5/001.
  15. ^ Matthews, Robert (20 December 2019). "Wormholes: Could we travel through a black hole into another galaxy?". Retrieved 13 June 2021.


  1. ^ Between small galaxies, which are the majority of galaxies, distances are typically a few hundred thousand light-years. Between large galaxies like the Milky Way and M31, they are typically a few million light-years.